In wireless communications, a user device may connect with a base station wirelessly. The user device may send data to and receive data from the base station over the wireless connection between them. When one party (e.g., either the user device or the base station) sends a data transmission to the other party (e.g., either the base station or the user device), the receiving party may send a response back to the sending party, indicating whether the data transmission has been successful. For example, if the data transmission is successful, the receiving party may send an ACK response back to the sending party. However, if the data transmission is not successful, the receiving party may send a NACK response back to the sending party, in which case the sending party may resend the data transmission to the receiving party.